1. Field of the Invention
The present invention relates to a test system used to align the boresite of a radar antenna. More particularly, the present invention relates to a test system to align the boresite of a collision avoidance radar system antenna with the thrust vector of an automobile.
2. Description of the Related Art
Recently, manufacturers have begun producing collision avoidance radar systems for automobiles. Such systems have been used in combination with a vehicle cruise control to form an automotive Adaptive Cruise Control (ACC) radar system. An ACC radar system transmits a signal from an antenna typically located in the grill area of an automobile. The ACC radar then determines from a return signal received by the radar antenna a distance an object causing the return signal is located from the automobile. If an object is detected in the path of the vehicle, wheel braking or engine deceleration is applied by the ACC radar system to maintain a desired distance from the object and to prevent the vehicle from striking the object.
To assure proper performance of an ACC radar system, the device must be regularly tested. During testing, proper alignment of the ACC radar antenna boresite with a thrust vector of the vehicle is assured. The vehicle thrust vector is typically identified along the forward direction of travel of a vehicle. To align the boresite of the ACC radar antenna, for FM-CW and Pulse modulated radar systems a Doppler shifted signal is not generally required for the radar, so a passive trihedral target reflector is typically used for testing and mechanically aligned at a point in space along the vehicle thrust vector. With the trihedral target so aligned, the position and orientation of the antenna are set to maximize the energy reflected back to the ACC radar from the trihedral target. Frequency shift keying (FSK) modulated radars require a Doppler shift in order for the radar to respond. To align the FSK radar along the vehicle thrust vector, either the vehicle must be moving relative to a trihedral target, or the target moving, and the antenna aligned to maximize reflected energy.
Also to assure proper performance, verification testing is performed to determine if the ACC radar system is making proper calculations of distance to an object creating a return signal.